IGF-1: a marker of individual life-span in a primate

The development of biological markers to evaluate individual life-span is badly needed because of the high cost and time duration that are necessary to assess the ageing process in long-living organisms such as primates. In this study, we measured insulin-like growth factor-1 (IGF-1) levels in a small, relatively short-living (maximal longevity: 12 years) primate from Madagascar, the gray mouse lemur (Microcebus murinus), in order to determine if they can be related to the rate of survival of this seasonal species. Cross-sectional blood samplings on 112 males of various ages indicated that IGF-1 levels remain high and constant during the long-day breeding seasons while a significant age-related decrease occurs from the fourth short-day resting season onward. Interestingly, in four-year-old lemurs, short-day IGF-1 body mass ratio values appeared as a good predictor of their life-span.